1. The Field of Invention
The present invention relates to centrifuge rotors and, more specifically, centrifuge rotors which can be sealed closed so as to prevent accidental dispersion of material held within the rotor during operation of the centrifuge.
2. The Relevant Technology
Centrifuges are used in a variety of different environments for facilitating such services as separating substances of different densities, removing moisture from materials, and for simulating gravitational effects. A conventional laboratory centrifuge includes a rotor housing which is attached to the drive shaft of a motor. The rotor body is configured to receive test tubes which hold a desired substance. As the motor is operated, the rotor is rapidly spun so as to produce an increased gravitational affect on the substance within the test tubes. Where the substance is a solution, the elements of the solution are then separated by density.
To increase the operational safety of centrifuges, a lid is typically removably secured to the rotor body. Should a test tube accidentally fail, the lid helps to prevent parts of the test tube and/or the substance it contains from being thrown or dispersed into the surrounding environment. This is particularly important where the centrifuge is spinning a hazardous substances.
Although lids are helpful in containing the substance of failed test tubes, it is still possible for the spilled substance to seep out at the joint between the lid and the rotor body. To help prevent leaking at the joint, attempts have been made to position a seal between the lid and rotor housing. The seals, however, are often distorted and fail under the tremendous centrifugal force applied thereto
In one attempt at incorporating a seal, German Patent No. 29 07 001 C2 and corresponding U.S. Pat. No. 4,202,487 disclose a rotor housing with a screw-on lid. A sealing O-ring is positioned along the periphery between the rotor housing and rotor lid so that the sealing action of the O-ring is reinforced when the centrifuge is in operation. That is, this arrangement generates a moment of rotation which produces a radial centrifugal force, and it also generates a sealing force in the axial direction. It thereby becomes possible to bring about a sealing with a reliable sealing action even if the lid is screwed on only loosely. Due to the construction of the rotor lid and the rotor housing, the O-ring is held in its correct position in order to obtain a favorable sealing during the centrifugation procedure.
Although useful, some problems have been shown to arise with the above arrangement. For example, O-rings require a relatively narrow tolerance range. In addition, the above assembly does not facilitate the collection of spilled fluids in the rotor.